Belt Tensioner for 5mm Gates Idler with adjusted belt path.

thingiverse

Human: I worked this up for myself a couple of months ago but never released it because I didn't want to muddy the waters with an adjusted belt path. When Prusa released the MK3S with the R4 Y-Idler, I compared mine to theirs and saw that I was only 2/10mm different from what they have. Since I'm happy with my belt path, I've decided to leave well enough alone, but also thought others might want this version. If you use this version, you really should change the Y-Belt holder as well because it too has been adjusted to maintain a horizontal belt path. I also posted the same tensioner with the idler pulley 2mm higher than the original Prusa location. See PDF for more details. Items You'll Need for This: (1) Gates 20T idler with a 5mm bore (1) 4.95mm diameter shaft that's 24mm long, (opening is 24.5mm so 24mm works just fine) (2) M3 x 20mm socket head cap screws, one for the pivot and one for the tensioner (2) M3 x 8mm socket head cap screws to mount tensioner to the frame (4) M3 hex nuts; you can use flats or Nylock but I see no reason to use Nylock nuts I included (2) .4mm washers to center the idler, not necessary but I prefer them. Note that the nuts are a tight fit; I do this to keep them from falling out but be prepared to put some effort into seating them, except for the tensioning nut slot. Print without supports and as oriented in the files, except the washers need to be properly oriented.